Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$199.75	4.408%	$208.555	$208.56	$208.55	$208.60
Purchase #2	$187.94	9.485%	$205.7661	$205.77	$205.75	$205.80
Purchase #3	$239.58	11.820%	$267.8984	$267.90	$267.90	$267.90
Purchase #4	$115.41	10.402%	$127.4149	$127.41	$127.40	$127.40
Purchase #5	$89.30	13.815%	$101.6368	$101.64	$101.65	$101.60
Purchase #6	$73.84	5.152%	$77.6442	$77.64	$77.65	$77.60
Purchase #7	$229.85	11.123%	$255.4162	$255.42	$255.40	$255.40
7 purchase totals =	$1,135.67		$1,244.3316	$1,244.34	$1,244.30	$1,244.30